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Drbelly

Belly's Obsy Build

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Well I have finally got the nod from the other half and found some time to start my own obsy build. I've been looking to do this for some time as lugging kit in and out every time was getting tedious especially when the clouds started to roll in just as I was about to start polar alignment.

I'm planning to build a ROR obsy with the total overal dimensions of 2.4 x 4.8M. This will likely be halved to create two equal rooms - one for the scope and one for me. I've been looking at various designs but I think I've settled on something similar to Malcolm's obsy with the pent roof over the scope room rolling over the warm room roof.

Manged to dig the footings for the pier a few days ago. This is 3' square and about 2.5' deep so should be enough.

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I've decided on a 160mm platic tube pier filled with concrete. I hamered 3 long 2m lengths of rebar a couple of feet into the bottom of the foundation hole then placed the tube over this. A couple of mixer loads of concrete into the job. Only about another 10 to go.

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A couple of hours later and the job is done but thats almost a ton of concrete to fill the foundations.

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So that's where I'm up to for now. I will be looking for lots of advice along the way from all you seasoned obsy builders. :)

Chris :)

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Thats a good start, and you have the hardest part, IMO, done now, the pier hole has been dug, the rest is a breeze!!

Looking forward to seeing how you get on.

Gary

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Looking good so far Chris, its going to be a nice size obsy.

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Looks like you have an excellent starting point with a nice flat and level plot. Good start and 2.4m x 4.8m will give you lots of space

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Looking good.

Time to start thinking about how to top off the pier. Any thoughts?

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Thanks everyone :)

Tom, I've been looking at some pier adapter plates from this site http://www.astroteclimited.co.uk/

They look pretty good and I think there's a discount for SGL members so may well go for them.

Graham, with regards timeframe I certainly hope to get things finished over the summer in time for the darker autumn skies but with a young family and busy job it's going to be a case of doing things bit by bit when I can get the time.

The next job will be deciding on the base. I'm leaning towards cementing in several breeze blocks to act as padstones and build a good solid wooden frame on these. I have about 20 odd breeze blocks already at home so wouldn't have to buy any which will help keep costs down. As to timber size for the floor if doing it this way does anyone have any suggestions from previous experience?

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Floor joists should be 6"x2" (150x47mm) at 16" (450mm) spacing, with noggins between to hold them straight and upright.

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As Gina says 6" x 2" one of the workshops i built had this base, along the bottom of the 6 by 2's i attached 2" by 1" roof battening and then place 1/4 ply on these filled the void with insulation then T & G flooring on top...

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Personally, as I've said in many a build thread, the foundation / floor is the key to a sound structure. If the floor is going to be suspended in any way, be that from joist hangers as per my build, or on blocks such as you suggest then 6" x 2" timbers at 16" centres is the way to go

attachment.php?attachmentid=59945&stc=1&thumb=1&d=1306957216

If you have a solid base (as per Waynes build) then the frame work need not be so sturdy as the frame is constantly supported by the base and thus distributes the weight without flexing.

Now this is not directed at anyone in particular, but is does niggle me somewhat when people start a build thread and then start compromising on the build and cut corners to save money, normally with the base / floor, which IMO is false economy. I've had four adults in the observatory and two in the warm room and the floor didn't even make a creek !!

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Agreed Malcolm :) I took your advice and didn't scrimp and very glad I did as I now have a very solid building that works well :)

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I'm in total agreement with you all that the foundations/floor need to be solid so 6x2" joists it will be. :)

I'm undecided as to how many padstones I should use? I could place 1 at each corner with a few along each perimeter and then use joist hangers to hang the joists across or add extra padstones at various points internally instead of using joist hangers to distribute the weight.

Thoughts everyone :)

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Chris, the more you use, the closer the spacing, the shorter the span between them, the better the weight distribution, the better the build :)

Assuming they are approx a foot square, for 6" x 2" joists and framework I would place them at around 1.25m apart. That would give you three along the 2.4m sections and 6 along the length. - 18 in total

Edited by malc-c

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Not a huge amount of progress but I have pegged out the site and set out some blocks that I propose to use as the padstones. These will be concreted in level. There is a slight slope down towards the hedge and chicken run so I'll have to be careful to get them level. I'll then build the floor on top of these using a 6"x2" frame with 6"x2" joists at 16" centers supported off the frame using joist hangers - something like the SketchUp model below.

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Edited by Drbelly

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Chris, that's one one tall pier! Are you imaging or observing?

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Chris, that looks the business. I would recommend cross-bracing between the joists just to tie it all together...

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Hi Petrol, I'm mainly into imaging. The pier tube is about 2+ metres high at present but will be cut down to size when I decide how tall it should be. Once the floor is done I can set up my mount on its tripod and experiment with various heights. I'm 6'2" so will want the obsy walls to be about 1.9-2 metres tall to prevent me having to stoop inside.

Thanks malcolm. I'll be placing noggins between all the joists to keep it nice and straight then like you probably cover it with marine ply.

With regards wall height, I'm not sure if I'm going to need a drop down flap to improve the views. The obsy is running basically north-south with south being at the short end towards the chicken run on the photos. I may contemplate a flap on the southern gable wall to aid viewing in this direction. What does everyone think?

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It depends on how high you have your pier. Best to get that sorted out first then you can see how high or low you want the walls. A good view to the south is particularly beneficial - more so than other directions - so you may well find a fold down flap would be helpful.

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You're right Gina. Until the pier height is known everything else is a bit uncertain. :(

I'm starting to look at getting quotes for the timber I need for the floor and walls. I'll be using CLS studwork to build the frames for the walls and roof sections. Can anyone give recommendations (or warnings) for various wood suppliers they have used?

I'll probably use OSB for the roof covered with either the rubber sheeting I've seen others use or may go for felt - not quite decided on that yet but plenty of time. :(

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Malcolm, I keep forgetting to ask, but what is the name of that insulation you used for your obsy floor and how much was it? Presumably you just used it under the warm room floor ?

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You're right Gina. Until the pier height is known everything else is a bit uncertain. :(

I'm starting to look at getting quotes for the timber I need for the floor and walls. I'll be using CLS studwork to build the frames for the walls and roof sections. Can anyone give recommendations (or warnings) for various wood suppliers they have used?

NOT Wickes - or other big DIY store. I used a local supplier and saved nearly half the price of Wickes also I got far superior timber.
I'll probably use OSB for the roof covered with either the rubber sheeting I've seen others use or may go for felt - not quite decided on that yet but plenty of time. :(
I used OSB for the warm room roof where weight wasn't a big problem but I used 6mm exterior plywood for the roll off roof on a timber framework for lighter weight for the strength. Yes, I used the rubber roofing - lighter and much easier to handle than felt. Cost a bit more but very much more durable and I would thoroughly recommend it.

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Malcolm, I keep forgetting to ask, but what is the name of that insulation you used for your obsy floor and how much was it? Presumably you just used it under the warm room floor ?

Chris,

Jablite - (http://www.diy.com/nav/build/insulation/constructional-insulation/flooring_insulation/Jablite-Flooring-Polyboard-L-2400-W-x-1200-x-T-50mm-9415189?icamp=recs)

I purchased it from B&Q, and yes used it for the floor, with standard 30mm styrene in the walls and ceiling of the warm room

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I have finally managed to progress a little with my build and have ordered a lot of the timber I'm going to need. I'm off work this week so hopefully will be able to get a fair bit done depending on the weather of course.

After working out where to have the padstones for the suspended floor to sit on I dug out the holes for the footings.

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To get the footings level I used pegs with marks measured from the top and used a long spirit level to get the top of the pegs level. I then poured concrete up to the mark on each peg so that I knew each footing was level with the rest. Once the footings had gone off I could then mortar in each block and made sure these were all level too.

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As you can see from the blocks there is a fair drop down to the bottom corner. I had to mortar in the blocks vertically instead of flat as originally planned on my model, because the top of the blocks closest to the camera would have been below ground level.

The floor joists, 18mm marine ply and CLS studwork has been delivered. I have given the 6x2" joists a coat of wood preserver and hopefully tomorrow will get the floor down. Fingers crossed it doesn't rain.

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I would find a local builders merchant to supply the CLS. They're not necessarily cheaper, but generally you seem to get better quality for your money.

James

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